Shorting switch



Aug. 22, 1967 1 BROTHERS 3,337,757

SHORIING SWITCH Filed Dec. ll, 1964 2 Sheets-Sheet 1 ATTORNEYS:

Aug. 22, 1967 1. BROTHERS SHORTING swITcH 2 Sheets-Sheet 2 Filed Dec. ll, 1964 /V/ze FIGS.

F D INVENTOR. IG 4 JAGK BROTHERS f) BY M1. f n zu? M i J ATTORNEYS:

United States Patent O 3,337,757 SHORTING SWITCH Jack Brothers, Succasunna, NJ., assigner to the United States of America as represented by the Secretary of the Army Filed Dec. 11, 1964, Ser. No. 419,282 2 Claims. (Cl. S10-8.4)

ABSTRACT OF THE DISCLOSURE A protective switch of the shorting-bar type is provided for a piezo-electric charge-generating device which is operated by inertial compressional force. The piezo-electric device is of Hat relatively-thin disk form and engaged by a at slotted fulcrum plate or disk through which an inertial shorting bar operates as part of a at relatively-thin shorting-bar plate or disk. The latter is compressed against the fulcrum plate to apply operating pressure to the piezoelectric device, by a relatively-thick body or inertial mass. These elements are preferably all of the same circular form and diameter to fit together in coaxial stacked contacting relation. The fulcrum plate is arranged, with the shorting-bar plate, to provide a xed fulcrum or pivot point for the shorting bar and accurately dene its active or operating length. Accuracy of operation is assured by this construction throughout any number of manufactured units.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

The present invention relates to piezo-electric apparatus for operation as electrical charge or pulse voltage sources in projectiles or missiles and other like carriers which are subject to explosive forces and extremely rapid acceleration on starting in flight. The piezo-electric device or cartridge in such apparatus is generally oriented with the axis or direction of tiight to receive by inertial setback, a compressional force sufficient to generate a desired Working charge therein up to a maximum safe limit. During the short periods of rapid acceleration, the compressional forces may become excessively high whereby this safe limit may tend to be far exceeded and result in overcharge or overvoltage output sullicient to cause damage to the crystal or piezoelectric element thereof or the connected circuit elements operating therewith.

During the short periods of rapid acceleration, as upon tiring of a projectile by which the apparatus is carried, the piezo-electric device must be protected against damage by overcharge or overvoltage conditions while providing in-liight charging and voltage supply at other times. Generally, momentary short circuiting of the piezo-electric device or cartridge is provided by switch means which includes an inertia-operated shorting bar connected therewith and movable into bridging contact with the output circuit thereof. It is to such protective switch means, for piezo-electric apparatus of the type described, that the present invention more particularly relates.

In prior known apparatus of this type, the shorting bar is generally a simple cantilever beam, round, square or rectangular in cross-section, affixed to a fulcrum or pivot point by staking, screws, pins or like means of attachment. Such apparatus is subject to erratic action due to lateral forces resulting from rotational acceleration, and differ` ences in -opefr'ational response of the shorting bar resulting from inaccuracy of the fulcrum or pivot point location.

Thus the piezo-electric device may not be protected fully or at the proper time.

It is therefore, a primary object of the present invention, to provide an improved piezo-electric apparatus, of the type referred to, which solves the problem of short-circuiting the piezo-electric device thereof more consistently and accurately than previously known apparatus of this type for operation as charged voltage sources in projectiles and other high-speed carriers subject to extremely rapid acceleration.

It is a further object of this invention, to provide an improved protective switch of the shorting-bar type in conjunction with a piezo-electric charge generating device which is operated by inertial compressional forces, provided in apparatus of the type referred to, that exceed safe limits in a moving carrier subject to extremely rapid acceleration, such as a missile or projectile.

It is also a further object of this invention, to provide improved protective switch means and piezo-electric device, in apparatus of the type referred to, of simplified, easilyassembled, structural and operational elements and wherein the fulcrum point and operating length of the shorting bar are accurately defined and easily reproduced in line or mass production, and wherein erratic action due to lateral forces and differences of operational response are eliminated.

In accordance with one form of the invention, the piezoelectric device or cartridge is engaged and compressed by a fiat fulcrum plate or disk through which the shorting `bar operates from a similar flat relatively-thin shorting-bar plate or disk that is, in turn, compressed flat against it by a relatively-thick plate or body of the same outside size or diameter providing an inertially-acluated mass for generating the desired compressional force. The fulcrum plate has a single transverse central or diametral slot extending from one edge, and registering with but shorter than the shorting bar to provide a fixed fulcrum or pivot point therefor and accurately define its active length for uniform inertial movement or response to accelerating forces above the safe operating limit.

The shorting-bar plate or disk provides the shorting bar and holder as one integral flat compression-transmitting element with the bar as a transverse central or diametral tongue between two spaced substantially-parallel slots extending therewith from one edge to a greater depth than the slot in the fulcrum plate with which the bar is aligned for shorting movement. A contact point at the free outer end of the bar moves to touch and bridge the piezo-electric device or cartridge as the bar bends from the fulcrum point through the slot in the fulcrum plate. Contact is made when the force of acceleration reaches or exceeds a predetermined high limit beyond which overcharge or overvoltage output could cause damage to the device per se or connected circuits.

This simplified shorting bar structure thus includes two slotted flat disks compressed against the piezo-electric device or cartridge, which may be relatively thin and disklike. Preferably these elements are circular in form to fit within a common thin-walled cylindrical container or envelope in stacked contacting relation, 4and are thus preferably of substantially the same outside diameter. These disks are readily made to uniform dimensions and at relatively low cost, and are easily assembled with the unit in stacked relation.

The accuracy of operation is assured at delinite safe limits of applied force, and resultant compression and charge, by reason of the fulcrum point and length of the shorting bar or cantilever being uniform and well defined throughout any number of manufactured units. The protective switch means is substantially uniform in construction and operation from unit to unit of this piezo-electric apparatus.

The invention will, however, be further understood from the following description of a present preferred embodiment thereof, when considered with reference to the accompanying drawings, and its scope is pointed out in the appended claims.

In the drawings:

FIG. 1 is a side view, in elevation, of a piezo-electric device for operation as a charged voltage source in a projectile or missile and provided with protective switch means embodying the invention,

FIG. 2 is an end view, in elevation, of the device of FIG. 1 further showing its construction,

FIG. 3 is a sectional side view, in elevation and on an enlarged scale from the preceding figures, of the device shown therein, taken on the section line 3-3 of FIG. 2, and further showing the construction in detail in accordance with the invention,

FIG. 4 is an end view, in elevation, of a shorting bar disk or element of FIG. 3, showing further details of construction, and

FIGS. 5 and 6 are end and side views, respectively, in elevation, of a fulcrum disk or element of FIG. 3, also showing further details of construction.

Referring to the drawings, wherein like elements and parts throughout the various figures are designated to by like reference numerals, and referring more particularly to FIGS. l and 2, a piezo-electric unit or apparatus for charge or voltage generation by inertial setback in a projectile or like carrier in flight is provided with a thinwalled cylindrical outer casing or envelope 11, the forward end of which is closed by a cover insulator plate of disk 12, locked in place by a screw-on cover element or cover 13 which is tightened down on a threaded central terminal pin 14 against it, as will hereinafter further be seen. An outer protective cylindrical split sleeve 15 of relatively tough insulating material snugly surrounds the casing 11 which is bell-shaped and crimped at the forward or open end as indicated.

The apparatus or unit is symmetrical about a central longitudinal axis indicated by the dash-and-dot line 16 in FIG. l, and, on operation, is oriented with the direction of flight or movement of the projectile or carrier, which is indicated by the arrowed line 17. Inertial forces due to acceleration are thus applied to the apparatus or unit along the axes 16 or in this axial direction.

Referring now to FIGS. 3, 4, 5 and 6 along with the preceding figures, the casing 11 is of a deep cup shape with its closed inner or bottom end to the rear with respect to the direction of movement on a carrier. Seated in contact with this inner end is a thin flat piezo-electric device or cartridge 18 having a crystal cup or holder 20 for the crystal element or wafer 21. The latter is of the usual thin, fiat, round or circular shape and seated on one face or side flat against uthe bottom of the holder 20 and contacted firmly on the other side by a crystal bearing plate or disk 22 for the application of operating pressure thereto.

The crystal or piezo-electric element is potted with casting resin or other suitable insulating compound providing an annular filler ring 23, as indicated, between the side wall of the cup 20 and crystal and bearing or pressure plate 22. The cup 20 is centered in the outer casing 11 by an inner split sleeve or tube 24 of insulating material and substantially uniform diameter and thickness to fit snugly in the casing and securely hold the cup and other elements assembled in stacked relation therewith along the axis of the device, as will appear.

The piezo-electric device or cartridge is engaged and compressed directly by a fulcrum plate or disk 26 chamfered, as indicated, on its rear or contacting face to clear the cup or crystal holder 20 and apply `pressure to the bearing plate 22. A second plate 27, which is the shorting bar plate or disk, is in direct pressure-transmitting contact with the disk 26 and is backed up or supported by a third plate or disk 28 in pressure transmitting contact therewith. These parts are of metal or suitable electrical conducting material to provide a connection from the negative face of the crystal 21 and the pressure plate 22 through the plates or disks 26 and 27 to the plate or disk 28. The positive face of the crystal is connected with the cup or holder 20 and through the latter to the outer casing 11 which preferably is of metal or other conducting material. In the present example the metal parts may be made of brass or mild steel. Copper beryllium alloy is preferred for the shorting bar disk 27.

As shown more clearly in FIGS. 4, 5 and 6, the fulcrum plate or disk 26 is a simple circular llat disk with a single central slot 29 and an edge notch 30 extending inwardly radially, or diametrally in the case of the slot, to a predetermined length or depth, the shorting-bar plate or disk 27 is a similar simple at disk with two parallel spaced slots 31 extending inwardly from one edge on either side of a relatively-wide central tongue or bar 32 integrally attached to the disk at its root or base end between the slots, and thus having a free outer end 33. Being wider than it is thick, it tends to bend in response to inertial forces applied along the axis 16 at a right angle or normal to the plane of the disk and to resist bending or like deflection in the plane of the disc. It is held in alignment or registration with the slot 29, by a deformable tab 35 provided in the edge of the disk 27 between two spaced short parallel slots 36.

The shorting-bar and fulcrum plates or disks are both simple flat disks, preferably circular and of like diameter, the first with two centrally-located parallel spaced slots extending in from the edge of the disk, and the second being the same but with one central diametral slot, wider than the space between the two slots, to provide clearance for the tongue or shorting bar when the two disks are stacked together on the piezo-electric device in the tube 24 as shown in FIG. 3 and the bar deects as hereinbefore indicated. For this, the single slot is also shorter than the two slots to provide a fixed fulcrum point or edge 38 at the bottom of the slot against which the bar can bend or pivot and by which its active length is defined sharply as will be described.

The remainder of the piezo-electric apparatus or unit 10 includes means adapted to apply pressure through the stack to the piezo-electric device by inertial setback, and suitable output switching and terminal means for withdrawing a charge or an operating voltage pulse from the charged element. To this end, the plate or disk 28 is directly contacted by and connected with a cylindrical switch or ball housing 39 which fits into the inner sleeve 24 as part of the stacked circular disk elements with the crystal element. This element is relatively thick and provides a mass for supplying the inertial force for compressing and charging the piezo-electric unit or device. Thus guided in the tube or sleeve 24, it applies compression to the plate 28 and thence to the stack and through to the crystal bearing plate 22.

The ball or switch housing 39 is provided with a central or axial cavity 40 which is tapered to a central forward opening 41 at its inner end. A switch ball 42 is freely mounted to move in the cavity and provide a conductive bridging connection between the ball housing and the central terminal pin 14 which projects through the opening 41 into the cavity as a contact element of the switching means. The forward end of the pin 14 is screwthreaded, as indicated, to receive and hold the cover 13 which is similarly threaded internally through a central beveled opening 43 in the hub 44.

The terminal pin 14 is rigidly mounted in a central insulator 45 in the axis of a circular terminal holder disk or plate 46 having a forward beveled or chamfered edge 47 over which the forward open end of the casing or envelope 11 is crimped to compress and hold the internal stacked elements together. The central insulator is provided with a metallic outer protective hub or flanged sleeve 48 which fits into the disk or plate 46. The cover 13 is screwed tight and clamps the interposed cover insulator 12 against the terminal holder assembly and provides a rigid unit that is adapted for rugged field use. The whole unit is provided with protective cover means by the split outer insulator sleeve 1S, and the cover may be locked to the pin by a body of solder 49 in the forward end of the bevel opening 43. As noted with reference to FIG. 3, the negative side of the piezo-electric wafer or crystal 21 is connected electrically directly to the bearing or pressure plate 22, while the positive side contacts and is connected electrically directly to the crystal holder or cup 20 and through it to the envelope or casing 11. From the casing an output connection may be made, as indicated by the output lead 50 representing any suitable output connection means therefrom.

In addition to the shorting bar 32, the negative output connection from the piezo-electric element 21 is made to the plate 28 which is interposed between the shortingbar holder or plate 27 and the ball or switch housing 39. Thus the series of stacked disk-like elements, including the housing 39, are connected with the negative side of the charge source or crystal 21. When the ball 42 closes with the pin 14 in contact with the housing 40, the pin provides a further connection to the cover 13. From the hub 44 or other suitable element of the cover a negative output connection may be made, as indicated by the connection lead 51 representing any suitable output connection means therefrom.

A piezo-electric unit or apparatus for voltage generation by inertial set-back in projectiles and other high speed carriers in flight is thus provided. A charge is generated as this compressional force along the axis of the unit increases on the piezo-electric device. This force is derived mainly from the inertia of the mass of the housing 4() and its closure plate 28. Setback or inertial force also acts upon the shorting `bar 32 and causes it to move rearwardly from the fulcrum or pivot point 38, as indicated in dotted outline 32', so that the contact point 33 approaches a contact point 55 on the rim or llange edge of the cup 20 in varying degrees while the compressional force and resulting charge are within safe limits or below a maximum safe level. The unit thus may generate and have ready a charge or voltage output for release and use at the proper time as when the switch means, comprising the ball and pin, may operate.

When the setback force reaches a maximum safe level, for example, 9000 Gs, the shorting bar 32 contacts the point 55 as indicated at 33', whereby the piezo-electric device 18 is short-circuited and the charge is removed. Thus the crystal 21 is protected against overcharge and damage at this or higher pressures since it remains short circuited and so can accumulate no charge until the shorting bar opens contact again. In some cases the set back force may go to 20,000' Gs for example, so that the charge could go destructively high without the shorting control. However, a useful working charge must be developed and retained following such periods of danger.

Thus the piezo-electric deivce remains shorted or inactive until the set back force is reduced and falls below the `maximum safe limit, for example 9000 Gs. Then the shorting bar moves away from the point 55, thus opening the short circuit and permitting a charge to generate as the normal inertial set back force is removed from the piezo-electric element. In projectiles and such carriers, the set back force acting on the piezo-electric device generally returns substantially to zero soon after the projectile or carrier has left the gun or other launching means by which an explosive driving force is applied. Thus the piezo-electric device is charged on set back through the use of this type of shorting switch and is ready to perform its normal and useful function as a charged pulse-voltage source in a projectile or like vehicle in flight after a high explosiveshock take off or like accelerating drive.

During such periods of rapid acceleration, the piezoelectric element may be protected against overcharge or overvoltage at the same limit or level of set back force in any one device uniformly throughout a production run of such devices. The shorting bar and holding means therefor are unitary and integral, being in each case a simple circular disk with two spaced parallel slots extending inwardly from one edge to the same depth to define the width and length of the shorting bar between them. The pivot or fulcrum means for the shorting bar is a second simple circular disk with a single slot extending inwardly from one edge to a depth less than the depth of the shorting bar slots and with the inner end thereof sharply delining the fulcrum or pivot point of the shorting bar and the active length from the pivot point to the free end thereof.

Both disks are essentially of the same diameter and aligned in coaxial stacked contacting relation with and between the piezo-electric device and the compression mass. The slots are aligned for free bending movement of the shorting bar through the single slot about the fulcrum point at the inner end thereof to bridge the piezoelectric device. While being part of the protective shorting switch means, these elements are also adapted thus to transmit compressional force to the piezo-electric element to charge it.

I claim:

1. A piezo-electric charge-generating apparatus for use in projectiles and like carriers, comprising in combination, a flat disk-like piezo-electric device, electrical terminal means for said device including a circular cup-shaped crystal holder and a circular bearing plate of electricallyconductive material, an electrically-conductive circular fulcrum plate in contact with said bearing plate for applying operating pressure thereto, said fulcrum plate having a transverse slot extending radially inwardly thereof from one edge for a predetermined length to provide a xed fulcrum edge at its inner end, a second relatively-thin electrically-conductive circular plate of like diameter in coaxial stacked relation and contact with the fulcrum plate providing an integral elongated shorting bar for the piezoelectric element in alignment with said slot and a contact point on said crystal holder, said second plate including two spaced slots extending from one edge in substantiallyparallel relation to define said shorting bar in width less than the width of the slot in the fulcrum plate and in length greater than the depth of said slot, and said shorting bar being in engagement with said fulcrum edge for movement thereon to close with said contact point in response to inertial force above an operating limit, and means providing an inertial operating mass connected with said second plate for applying said operating pressure therethrough to the bearing plate to charge said crystal in response to inertial force below said limit, said last-named means comprising a circular switch housing of like diameter as and greater thickness than said plates.

2. A piezo-electric charge-generating unit for use in projectiles and like carriers, comprising in combination, a flat circular disk-like piezo-electric device positioned for compressional charging operation in response to inertial pressure in the direction of the axis of Hight, a rst electrically-conductive circular disk in contact and coaxial with said device for applying operating pressure thereto, said disk having a transverse slot extending inwardly thereof from one edge for a predetermined length to provide a xed fulcrum edge at its terminal end, a second electrically-conductive circular disk of like diameter in stacked coaxial registration and contact with the rst disk, said second disk having two substantially-parallel spaced slots extending inwardly from one edge to define an elongated integral shorting bar in alignment with and of less width than the slot in the first plate, said shorting bar being 0f 3,337,757 7 8 greater length than the depth of the slot and engaging the said device to induce a charge thereon below said operatfulcrurn edge short of its base end to establish a fixed ing limit. operating length therefor, said bar being aligned at its free end with said piezo-electric device to move on said ful- References Cited Crum edge into shorting contact therewith in response to 5 UNITED STATES PATENTS inertial force above a predetermined normal compressional 3 098 163 7/1963 Bliss 10240 2 X operating limit for the piezo-electric device, and a circular switch housing in said unit providing an inertial operating BENJAMIN A BORCHELT Primary Emmi-nen mass coaxially aligned and connected with the second disk for applying said inertial compressional pressure to the lo W- C ROCH Ammin Examine"- 

2. A PIEZO-ELECTRIC CHARGE-GENERATING UNIT FOR USE IN PROJECTILES AND LIKE CARRIERS, COMPRISING IN COMBINATION, A FLAT CIRCULAR DISK-LIKE PIEZO-ELECTRIC DEVICE POSITIONED FOR COMPRESSIONAL CHARGING OPERATION IN RESPONSE TO INERTIAL PRESSURE IN THE DIRECTION OF THE AXIS OF FLIGHT, A FIRST ELECTRICALLY-CONDUCTIVE CIRCULAR DISK IN CONTACT AND COAXIAL WITH SAID DEVICE FOR APPLYING OPERATING PRESSURE THERETO, SAID DISK HAVING A TRANSVERSE SLOT EXTENDING INWARDLY THEREOF FROM ONE EDGE FOR A PREDETERMINED LENGTH TO PROVIDE A FIXED FULCRUM EDGE AT ITS TERMINAL END, A SECOND ELECTRICALLY-CONDUCTIVE CIRCULAR DISK OF LIKE DIAMETER IN STACKED COAXIAL REGISTRATION AND CONTACT WITH THE FIRST DISK, SAID SECOND DISK HAVING TWO SUBSTANTIALLY-PARALLEL SPACED SLOTS EXTENDING INWARDLY FROM ONE EDGE TO DEFINE AN ELONGATED INTEGRAL SHORTING BAR IN ALIGNMENT WITH AND OF LESS WIDTH THAN THE SLOT IN THE FIRST PLATE, SAID SHORTING BAR BEING OF GREATER LENGTH THAN THE DEPTH OF THE SLOT AND ENGAGING THE FULCRUM EDGE SHORT OF ITS BASE END TO ESTABLISH A FIXED OPERATING LENGTH THEREFOR, SAID BAR BEING ALIGNED AT ITS FREE END WITH SAID PIEZO-ELECTRIC DEVICE TO MOVE ON SAID FULCRUM EDGE INTO SHORTING CONTACT THEREWITH IN RESPONSE TO INERTIAL FORCE ABOVE A PREDETERMINED NORMAL COMPRESSIONAL OPERATING LIMIT FOR THE PIEZO-ELECTRIC DEVICE, AND A CIRCULAR SWITCH HOUSING IN SAID UNIT PROVIDING AN INERTIAL OPERATING MASS COAXIALLY ALIGNED AND CONNECTED WITH THE SECOND DISK FOR APPLYING SAID INERTIAL COMPRESSIONAL PRESSURE TO THE SAID DEVICE TO INDUCE A CHARGE THEREON BELOW SAID OPERATING LIMIT. 